Those provisions would leave unaltered the power of the Federal Bureau of Investigation (FBI) to seize records and to eavesdrop on phone calls and e-mail in the course of counter-terrorism investigations.

The parts of the act due to expire on Dec. 31 deal with:

National Security Letters (NSLs)

The FBI uses NSLs to compel Internet service providers, libraries, banks, and credit reporting companies to turn over sensitive information about their customers and patrons. Using this data, the government can compile vast dossiers about innocent people.

The 'Material Support' Statute

This provision criminalises providing "material support" to terrorists, defined as providing any tangible or intangible good, service or advice to a terrorist or designated group. As amended by the Patriot Act and other laws since Sep. 11, this section criminalises a wide array of activities, regardless of whether they actually or intentionally further terrorist goals or organisations.

FISA Amendments Act of 2008

This past summer, Congress passed a law that permits the government to conduct warrantless and suspicion-less dragnet collection of U.S. residents' international telephone calls and e-mails.

Asked by IPS why committee chairman Senator Patrick Leahy of Vermont and other Democrats chose to make only minor changes, Chip Pitts, president of the Bill of Rights Defence Committee, referred to "the secret and hypocritical lobbying by the Obama administration against reforms – while publicly stating receptiveness to them."

White House pressure, he speculated, "was undoubtedly a huge if lamentable factor".

He added that some committee members were cautious because of the recent arrests of Najibullah Zazi and others.

Zazi , a citizen of Afghanistan and a legal U.S. resident, was arrested in September as part of a group accused of planning to carry out acts of terrorism against the U.S. Zazi is said by the FBI to have attended courses and received instruction on weapons and explosives at an al Qaeda training camp in Pakistan.

Leahy acknowledged that, in light of these incidents, "This is no time to weaken or undermine the tools that law enforcement relies on to protect America."

Pitts told IPS, "Short-term and political considerations driven by dramatic events once again dramatically affected the need for a more sensible long-term, reasoned, rule-of-law approach."

"In the eight years since passage of the original Patriot Act, it's become clear that the escalating political competition to appear tough on terror - and avoid being accused of being "soft on terror" - brings perceived electoral benefits with few costs, with vital but fragile civil liberties being easily sacrificed," he added.

In contrast to the Senate, the House of Representatives Judiciary Committee approved a version of the legislation containing several significant reforms. In a 16-10 party-line vote, the committee's version curbs some of the government's controversial surveillance powers.

The Patriot Act, passed by a landslide after the 9/11 terrorist attacks to provide law enforcement and intelligence agencies additional powers to thwart terrorist activities, was reauthorised in 2005.

The legislation has been criticised by many from across the ideological spectrum as a threat to civil liberties, privacy and democratic traditions. Sections of the original act have been ruled unconstitutional, with certain provisions violating protected rights.

Judiciary Chair John Conyers, a Michigan Democrat, said the goal of the new legislation was to "craft a law that preserves both our national security and our national values".

The proposed new legislation would permit the so-called "lone wolf" provision to sunset. This authority removed the requirement that an individual needed to be an agent of a foreign power to be placed under surveillance by intelligence officials and permitted surveillance of individuals with a much lower evidentiary threshold than allowed under criminal surveillance procedures.

It was intended to allow the surveillance of individuals believed to be doing the bidding of foreign governments or terrorist organisations, even when the evidence of that connection was lacking.

The Justice Department maintains that the "lone wolf" authority is necessary, even though there is no evidence that it has been used. Its opponents believe that existing authorities are sufficient to achieve the goals of the lone wolf provision while more effectively protecting the rights of innocent citizens.

The proposed new House legislation would also restrict the use of national security letters. According to a Congressional Research Service report, "National security letters (NSL) are roughly comparable to administrative subpoenas. Intelligence agencies issue them for intelligence gathering purposes to telephone companies, Internet service providers, consumer credit reporting agencies, banks, and other financial institutions, directing the recipients to turn over certain customer records and similar information."

Under current law, intelligence agencies have few restrictions on the use of NSLs, and in numerous cases, have abused the authority. An FBI inspector general report in 2007 "found that the FBI used NSLs in violation of applicable NSL statutes, Attorney General Guidelines, and internal FBI policies". The reform provisions seek to create greater judicial scrutiny of NSL use.

The bill approved in the Senate contains much more modest reforms. It would retain the lone wolf provision, and is, in general, much more in line with the wishes of the administration. Should both bills pass and go into conference to be reconciled, it is unclear which approach would prevail.

House and Senate versions still need to be voted on by each body separately and then reconciled into a single bill to send to the president for signature.

Pitts told IPS, "President Obama's flip-flop on Patriot Act issues does as much damage as did his flip-flop on the FISA Amendments Act and telecom immunity last year. But it's imperative that we fight, while we still can, to comprehensively reinsert requirements for fact-based, individualised suspicion, checks and balances, and meaningful judicial review prior to government intrusions."

In a report on the Patriot Act, the American Civil Liberties Union (ACLU) said, "More than seven years after its implementation there is little evidence that the Patriot Act has been effective in making America more secure from terrorists. However, there are many unfortunate examples that the government abused these authorities in ways that both violate the rights of innocent people and squander precious security resources."